Various aspects of the decision-making process, such as attention, perception, valuation, and preferences, are abnormal in neuropsychological disorders. However, the neural machinery that mediates decision- making is poorly understood. Increased understanding of normal and altered components of decision- making has the potential to improve our understanding and treatment of diseases such as autism, schizophrenia, and addiction. The posterior cingulate cortex (CGp), an area of cortex with extensive connections to both decision-making (attentional, motivational) and visuomotor circuitry, responds to visual stimuli associated with rewards. Recent observations from our lab show that posterior cingulate neuronal activity is modulated by both reward magnitude and reward variance, in economic terms risk. These observations suggest that posterior cingulate cortex may respond to salient, or motivationally significant, events independent of overt orienting and, furthermore, that CGp neuronal activity should predict behavioral sensitivity to changes in external and internal decision-making contexts. By investigating these hypotheses, we aim to link neuronal activity with either external contextual variables like risk and relative expected value or components of the internal context such as serotonin and dopamine activity. We will use a series of visuomotor tasks to determine whether CGp responds to salient events in the absence of choice, visual saccades, or visual cues. We will then use a simple choice task to investigate the correlation between CGp activity and behavioral responses to changes in both external and internal variables. We will use well-established dietary depletion methods to modify the internal serotonergic and dopaminergic components of the internal neurochemical milieu. We are currently studying the basic neural mechanisms of decision-making by measuring activity from neurons in the posterior cingulate cortex of the brain in macaques performing eye movement-based tasks for fruit juice rewards. Decision-making is dysfunctional in diseases like schizophrenia, autism, addiction, and pathological gambling. Therefore, a better understanding of decision-making processes will improve our understanding of these neuropsychological diseases and contribute to the development of better treatments. [unreadable] [unreadable] [unreadable]